Gujin yinshi 古今印史 "History of Ancient and Modern Seals" is a book on ancient seals written during the Ming period 明 (1368-1644) by Xu Guan 徐官 (fl. 1569), courtesy name Yuanmao 元懋. He hailed from Wuxian 吳縣 (modern Suzhou 蘇州, Jiangsu) and was a secretary of the Confucian teacher Wu Jiao 魏校. His dates of life are unknown apart from the information that he participated in the compilation of Wu Jiao's book Liushu jingyun 六書精蘊 as an expert for the large seal script (zhouwen 籀文) and the ancient script (guwen 古文). He also wrote the books Jingzhuan zuanyan 經傳纂言, Xianzhong jiwen 閑中紀聞 and Xiaojing guwen jicheng 孝經古文集成.
Yet a closer inspection of his texts show that Xu Guan's expertise was not very deep-going. He relied on bronze vessel inscriptions and took not into consideration the seal script used of the Han period 漢 (206 BCE-220 CE), where it was common to replace characters by other words in a kind of wordplay, like 劉 instead of 鎦, or 鳳 instead of 朋, and that in later times the play with homophones was very common, so that Zhuge Liang 諸葛亮 (181-234) might be written 諸葛諒 or Han Yu 韓愈 (768-824) rendered as 翰瘉. He also alleges to quote from the text Cangjiepian 蒼頡篇 that was long lost at that time. He also errs in his statement that the brothers Xu Kai 徐鍇 (920-974) and Xu Xuan 徐鉉 (916-991), commentators to and publishers of the Han-period dictionary Shuowen jiezi 說文解字, lived during the Song period 宋 (960-1279). Quite strange is his opinion that the characters of the chancery script (lishu 隸書) would have to be adapted to the small seal script shape, which would mean that all Han- and Wei-period 曹魏 (220-265) inscriptions were written with wrong characters.
Because of these many errors, the book was not included in the imperial series Siku quanshu 四庫全書, but it is to be found in the series Guang baichuan xuehai 廣百川學海, Baoyantang miji 寶顏堂秘笈, Zhuanxue suozhu 篆學瑣著 and Congshu jicheng 叢書集成.